OdysseyTwo

Elemental Ignore is fully known as Ignore Enemy Elemental Resistance, which very often gets confused with the Player's Elemental Resistance Stat. To eliminate this confusion, Elemental Ignore should be renamed to Elemental Penetration a la Path of Exile.

If you receive a node that is not compatible with your class, it should automatically be disassembled.

Not a bug. Carrion Breath is a Poison element attack skill and all monsters inside Cursed Temple, except Wild Kargo, are immune to the Poison element. I suggest you use a different attack skill against them. As a bonus, if you level your Insight trait to level 10, your Carrion Breath will now be able to deal more than 1 damage to the Poison immune monsters, but it will be very minuscule compared to using your other attack skills.

How Elemental Resistance works is it reduces damage taken from enemy attacks with elemental properties, which nowadays only implies the Poison Abnormal Status, enemy Poison Mists and similar, and most of Horntail's attacks. This makes Elemental Resistance is the least applicated character stat. Therefore, all Elemental Resistance effects should be changed to Damage Reduction effects, because most endgame bosses are resistant to physical (non-elemental) attacks, greatly reducing damage taken. Of course, if we convert Elemental Resistance to Damage Reduction 1:1, it would cause a major imbalance, so the values would have to be greatly reduced to keep them balanced.

The only classes, that are also available in KMS, whose unstackable Link Skills only have a max level of 2 are Cadena, Illium, Kinesis, Shade, and Xenon. I feel that adding level 3 to their Link Skills wouldn't cause too much power creep.

Cadena: Level 3 would imply 9% Damage per condition met, adding up to 18% Damage with both conditions. Although 18% Damage looks too OP for a Link Skill, there are 2 pieces of evidence that would push for a level 3. One, Demon Avenger's Link Skill has a level 3 that gives 15% Damage, only 3% less than Cadena's hypothetical level 3 link. And two, regular Damage has diminishing returns, meaning it's less effective the more regular Damage you have prior to activating Cadena's link.
Illium: Level 3 would imply 3% Damage per stack, adding up to 18% Damage at max stacks. See my argument with Cadena's link.
Kinesis: Level 3 would imply 6% Critical Damage. Before the V update, level 3 would have implied 12% Minimum Critical Damage, which would have been too OP, because most classes would only have a 3% Crit Damage difference, resulting in extremely consistent critical hits. With the Min Crit and Max Crit merge, the Crit Damage difference is always 30%, which made it strictly worse for most classes. Therefore, 6% Crit Damage wouldn't be very OP.
Shade: Level 3 would imply 15% Death Ignore Chance. 10% is the same rate as the most common success rate on Clean Slate Scrolls, and we all know how long and expensive it is to recover 1 upgrade slot. 15% is the same rate as the Weapon Spell Trace Scroll with the most amount of ATT, and it's barely easier than 10% CSS. Therefore, 15% Death Ignore Chance wouldn't be too OP.
Xenon: Level 3 would imply 15% All Stats. When Xenon was first released, GMS declared that his Link Skill at level 3 would be too OP. But one thing to keep in mind is his Link Skill has diminishing returns. Meaning the more All Stat percentage boost you have without his Link Skill, the smaller your overall All Stat increase will be when you activate his Link Skill. I feel that diminishing returns would make 15% All Stats not as OP as people would think.

As a bonus, Hayato and Kanna's Link Skills should also have a level 3, since I heard TMS was supposed to have level 3 added to them.

Hayato: Level 3 would imply 35 All Stat and 25 Weapon/Magic ATT. Diminishing returns says hi.
Kanna: Level 3 would imply 15% Damage. Literally the same as Demon Avenger's Link Skill.